1. Technical Field
The present invention relates to color cathode ray tubes, and more particularly, to a mask which is installed adjacent to a fluorescent film within the panel of a cathode ray tube and performs a color selection function, a manufacturing method thereof, and an exposure mask for manufacturing the shadow mask.
2. Related Art
In color cathode ray tubes (CRTs), which are used in the monitors of typical computers, televisions and the like, three electron beams emitted from an electron gun pass through the electron beam pass holes of a mask having a color selection function and land on red, green and blue fluorescent materials of a fluorescent film formed on the screen surface of a panel, thereby exciting the fluorescent materials to thus form an image.
In the above-described cathode ray tubes for forming pictures, masks having a color selection function include dot masks adopted in the monitor of computers and slot masks (or slit masks) used in televisions or the like.
A slot mask is designed to have the same curvature as a screen surface in consideration of landing of deflected electron beams. A mask as described above is obtained by forming a plurality of electron beam pass holes by etching a 0.1 to 0.25 millimeter (mm) thin plate, and molding the thin plate at a predetermined curvature. If the mask does not have a curvature equal to or greater than a predetermined level, it is permanently plastic-deformed in many cases during the manufacture of a cathode ray tube due to a decrease in the structural strength. As a result, there are many cases in which the mask cannot perform its unique color selection function. Also, as the incidence angle of electron beams passing through the slot increases, the amount of beams passing through the slot decreases.
Methods of manufacturing masks are disclosed in U.S. Pat. No. 4,094,678 to Palac, entitled METHOD OF MAKING CURVED COLOR CATHODE RAY TUBE SHADOW MASKS HAVING INTERREGISTRABLE ELECTRON BEAM-PASSING APERTURE PATTERNS, issued on Jun. 13, 1978 and in U.S. Pat. No. 4,210,843 to Avadani, entitled COLOR CRT SHADOW MASK AND METHOD OF MAKING SAME, issued on Jul. 1, 1980. The disclosed method of manufacturing masks adopts photolithography.
While these recent efforts provide advantages, we note that they fail to adequately provide an efficient and convenient manufacturing method for manufacturing an improved mask for a color cathode ray tube, and fail to adequately provide an efficient and convenient exposure mask for manufacturing the improved mask.
To solve the above problems and others, an objective of the present invention is to provide a method of manufacturing a mask for a color cathode ray tube, by which a restriction on the formation of slots and bridges by the thickness of a thin film can be reduced.
Another objective of the present invention is to provide an exposure mask used to perform a method of manufacturing masks.
To achieve these and other objects in accordance with the principles of the present invention, as embodied and broadly described, the present invention provides a mask for a color cathode ray tube, the mask including: a plurality of strips isolated from each other at predetermined intervals in parallel; and a plurality of bridges which connect adjacent strips to each other, are indented a predetermined depth from their upper surfaces, and thus form slots through which electron beams pass.
To achieve these and other objects in accordance with the principles of the present invention, as embodied and broadly described, the present invention provides a mask for a color cathode ray tube, the mask including: a plurality of strips isolated from each other at predetermined intervals in parallel; and a plurality of bridges for forming slots through which electron beams pass by connecting adjacent strips to each other. In this mask, each of the bridges between adjacent strips has a first curved portion formed on the side from which electron beams come out, and a second curved portion formed on the side upon which electron beams are incident. The first curved portion has a first width in the direction perpendicular to the length direction of the strips, and extends in the length direction of the strips. The second curved portion has a second width that is smaller than the first width in the length direction of the adjacent strips.
To achieve these and other objects in accordance with the principles of the present invention, as embodied and broadly described, the present invention provides a method of manufacturing a mask for a color cathode ray tube, the method including: coating the upper and lower surfaces of a thin plate with photosensitive films; arranging an upper exposure mask on the upper surface of the thin plate, the upper exposure mask having an exposure pattern in which first light transmission strips are formed in parallel to each other; arranging a lower exposure mask on the lower surface of the thin plate, the lower exposure mask having an exposure pattern in which second light transmission strips are formed in parallel to each other, and light blocking bridges are formed; exposing the photosensitive films to light in a state where the upper and lower exposure masks are arranged on the thin film; separating the upper and lower exposure masks from the thin plate, and developing the photosensitive films on the thin plate; etching the thin plate, the photosensitive films on which have been developed; and molding a mask to have a predetermined curvature.
To achieve these and other objects in accordance with the principles of the present invention, as embodied and broadly described, the present invention provides a mask for a color cathode ray tube, the mask comprising: a plurality of strips being parallel to each other, being isolated from each other, and being located at predetermined intervals; and a plurality of bridges connecting adjacent ones of said strips to each other and forming slots penetrated by electron beams, said bridges being indented to a predetermined depth from an upper surface of said bridges so that a thickness at a central portion of said bridges is relatively thinner than a thickness at an outer portion of said bridges.
To achieve these and other objects in accordance with the principles of the present invention, as embodied and broadly described, the present invention provides a method of manufacturing a mask for a color cathode ray tube, the method comprising: coating upper and lower surfaces of a thin plate with photosensitive films; arranging an upper exposure mask on said upper surface of said thin plate, said upper exposure mask having an exposure pattern with upper light transmission strips being formed in parallel to each other; arranging a lower exposure mask on said lower surface of said thin plate, said lower exposure mask having an exposure pattern with lower light transmission strips being formed in parallel to each other, and having lower light blocking bridges separating said lower light transmission strips; exposing said photosensitive films to light in a state where said upper and lower exposure masks are arranged on said thin plate; separating said upper and lower exposure masks from said thin plate, and developing said photosensitive films on said thin plate; when said developing of said photosensitive films is performed, etching said thin plate; and molding a mask to have a predetermined curvature.
To achieve these and other objects in accordance with the principles of the present invention, as embodied and broadly described, the present invention provides an exposure mask assembly, comprising: an upper exposure mask being closely attached to an upper surface of a thin plate, said upper surface being coated with photosensitive films, said upper exposure mask having an exposure pattern with upper light transmission strips being formed in parallel to each other; and a lower exposure mask being closely attached to a lower surface of said thin plate, said lower surface being coated with photosensitive films, said lower exposure mask having an exposure pattern with lower light transmission strips being formed in parallel to each other, and having lower light blocking bridges separating said lower light transmission strips, said lower light blocking bridges blocking light; said photosensitive films on said upper and lower surfaces being exposed to light penetrating said upper and lower exposure masks through said upper and lower light transmission strips, respectively.